Basic Input/Output System

  • BIOS is a program(Basic input/output system) which is stored in non-volatile memory like ROM (Read Only Memory) or flash memory.
  • It allows you to set up and access your computer system at the greatest basic level.
  • It is found on motherboards that are a pre-installed program on Windows-based computers that executes when a computer is powered up.
  • Before an OS is loaded, the CPU accesses the basic input/output system (BIOS).
  • Then, the next function of BIOS is to examine all the hardware connections and detects all your devices.
  • The main function of BIOS is to set up hardware and start an OS.
  • And it contains generic code that is needed to control display screens, the keyboard, and other functions.
  • The BIOS is built-in software that manages the hard drives and cannot live on one.
  • It cannot reside in the RAM (Random Access Memory) as it is accessible before the computer system boots up.
  • It lives on the ROM of the computer system, and mainly it is located on EPROM (erasable programmable read-only memory) chip.
  • Therefore, the CPU accesses the EPROM when you turn on the computer and provides control to the BIOS.
  • The primary intention of designing the BIOS system is to function with numerous devices.
  • There are some functions contained by the BIOS library that operates and controls system peripherals, and they can be initiated through external software.
  • Users can perform different functions by using the BIOS user interface:
  • Users can perform hardware configuration.
  •  They can select boot drives
  •  They can set the system clock
  •  The BIOS allows users to enable and disable certain system components
  •  To BIOS user interface function, it provides set password prompts for secured              access
  • The BIOS works as an intermediary between the I/O devices and the CPU and is used after the computer has booted up.
  • Our operating system and programs do not need to know the details about the I/O devices connected to your system because of the BIOS.
  • We can change these settings accordingly with the help of entering the BIOS setup at the time of your system starts up.
  • And if you want to access the BIOS setup,  can be done by holding down the DELETE or F2 key (or any other as per OEM) when our computer starts up.
  • BIOS is stored in rewritable memory in some modern PCs, which allow information to be replaced or rewritten.
  • Such content rewriting is executed with the help of a special program offered by system manufacturers.

BIOS Availability

  • The BIOS software is available in all modern computer motherboards.
  • As the BIOS is a part of the motherboard; therefore, the BIOS’s access and configuration on PCs are independent of any type of operating system.
  • The BIOS is not dependent on anyone that means it does not matter which types of an operating system is running on the computer like Windows 7, Windows 8, Windows 10, Windows XP, Linux, Windows Vista, Unix, or no operating system at all, BIOS functions outside of the operating system environment.


  • In BIOS software we can find the program that gives a computer a directions to load basic hardware.
  • And a test called POST (Power-On Self-Test) runs during boot up and thus helps the computer verifying the requirements properly of it.
  • And also the computer produces various forms of beeps if the POST test fails at the time of test.


  • The BIOS has different instructions that are required to load the hardware, and it is responsible for loading the operating system. The major functions of a Basic input/output system (BIOS) are :
  • BIOS Power on Self-Test (POST): It ensures the proper functioning of the computer hardware as it is a built-in diagnostic program.
  • It verifies the computer meets the necessary parts and functionality(POST)
  • It ensures that the computer is loading tasks successfully, such as the use of memory, a keyboard, and other parts when it starts up.
  • If the POST test fails at the time of test, the computer provides a combination of beeps to display the error type, and the system continues to boot when the POST test is passed completely.
  • Once the self-test has been passed à and the basic instructions have been loaded à the computer starts to load the OS from one of the connected drives to the system.
  • The BIOS settings can also be changed by the computer users with the help of a configuration screen on the computer.
  • The BIOS information can also be stored on the flash memory, which can be updated by computer users after releasing an update by vendors.

Bootstrap Loader:

  • The BIOS recognizes and locates the operating system when the POST running successfully.
  • The program bootstrap loader is contained by BIOS, which searches and starts the OS boot program.
  • When BIOS detects one, it transfers access to Operating System that is known as booting.

BIOS drivers: 

  • BIOS drivers are stored in the non-volatile memory, whose primary function is to supply basic computer hardware information.

BIOS Setup Utility Program: 

  • It is a configuration software, also known as CMOS setup, that allows users to configure hardware settings as well as device settings, time and date, computer password.
  • The NVRAM, non-volatile memory, is used to store settings of memory, disk types, and information about the computer system; this information is not stored in the BIOS chip
  • The users run the BIOS setup program during the installation of a system and input the correct parameters.
  • The CMOS (Complementary metal-oxide-semiconductor) is a required material to construct NVRAM.
  • These CMOS chips store and maintain data on very low values of current.
  • Therefore, the system’s configurations are also called CMOS settings.
  • With the help of using a capacitor, maintaining the battery backup, or by a battery built into the NVRAM chip, CMOS settings can be maintained.
  • Additionally, a system clock is also included in this chip.
  • The setting remains for a short period of time if there is no battery.
  • And there is a need to reset the system. Through its BIOS set up program is protected as there is loss of BIOS password.
  • With computers, BIOS come in-built as firmware on a chip on the motherboard.
  • An operating system such as iOS or Windows can be installed by the user or pre-installed by the vendor or manufacturer.
  • When BIOS boots up a computer, it verifies the computer meets the necessary attachments to boot up.
  • The files are contained by any piece of hardware that needs for a computer to start up, this piece of hardware is known as a boot device.

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